This invention relates generally to pulse generators, and, more particularly, to a very fast, variable interval, electromagnetic pulse train generator which relies upon controlled optical pulses to control the duration of each pulse and the interval of time between pulses.
Pulse generators have been in existence for many years. Generally, pulse generators provide wide band, short period, high power level outputs. The emphasis in past pulse generators was to simply obtain a short pulse with a fast current acceleration. In such generators, the energy was stored, dumped therefrom, and the results measured. Generating a closely spaced pulsed train was, in most instances, not essential, and generating a variable voltage and variable interval pulse train was definitely not considered for high power levels. Examples of typical pulse generators are as follows:
(a) The wave form synthesizer. This type of pulse generator was primarily developed for laboratory applications, was dependent upon to digital to analog conversion and was of low power. If such synthesizers were coupled to a high powered amplifier, the amplifier would have to be a narrow band device which would not be efficient for wide band signals.
(b) The Blumlein line. This type of generator is in the form of a transmission line attached to a cavity device such as a magnatron. An antenna in the transmission line is located at a null point in the standing wave. When the line is suddenly shortened, by closing a switch, a standing wave moves to the antenna and produces a short, high level dump of energy. This action can produce short, several cycle, pulses of sinusoidal energy at high levels. Such a device cannot vary the center frequency of the signal.
(c) The frozen Hertzian generator. This is another device for generating pulses with large relative band widths. At the present time, frozen Hertzian generators use only one or two switches and a single high voltage supply. The frozen Hertzian generator yields a single pulse or square wave cycle electric field which propagates down a transmission line to an antenna.
(d) The Marx generator. This device is capable of producing high voltage pulses by charging capacitors in parallel and then discharging them in series. Presently the switching action depends upon the utilization of spark gaps. The Marx generator is an example of a generator which provides raw power pulses.
U.S. Pat. No. 3,484,619 issued on Dec. 16, 1969 to Joseph M. Proud, Jr. is cited as an example of a radio frequency generator, while U.S. Pat. No. 4,329,686 issued May 11, 1982 to Gerard Mourou is cited as an example of an apparatus of generating microwave pulses. Both of these generators are also illustrative of the type of pulse generators in use today.
With the development of non-sinusoidal radar, it has become necessary to incorporate therein pulse generators capable of producing very fast electrical pulses, that is, very short duration (approximately 2 ns) pulses with picosecond rise times. Unfortunately, pulse generators of the past and of the type described above have several shortcomings, especially in the production of very fast, variable interval, electromagnetic pulse trains. The present invention sets forth a pulse generator which overcomes these shortcomings.